<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script src="jquery-3.4.1.js" type="text/javascript" charset="utf-8"></script>
		<script type="text/javascript">
			$(function(){
				
				$("#btn1").click(function(){
					$("#div1").css({
						"width":"400px",
						"height":"400px",
						"background-color":"red"
					})
					
				})
			})
			
		</script>
	</head>
	<body>
		<button type="button" id="btn1">按钮</button>
		<div id="div1" style="background-color: black; width: 40px; height: 40px;">
			
		</div>
	</body>
</html>
